title: [Rare anatomical variation of absence of the sciatic nerve: completely substituted by the tibial and common fibular nerve].
abstract: BACKGROUND
  There are several reports of sciatic nerve anatomical variations. Some are associated with clinical entities, such as piriformis syndrome. We aim to report a rare anatomical variation of this nerve.
  
  
  METHODS
  Two leucodermic, 74 and 78-year-old male subjects, deceased of natural causes, without lower limb relevant medical history. In both subjects, the right sciatic nerve was absent, with an independent origin and course of the tibial and common fibular nerves. The contralateral sciatic nerve had the common anatomical presentation.
  
  
  CONCLUSIONS
  After the analysis of the available data indexed in Medline, we conclude that we are reporting two cases of a rare anatomical variation (the absence of sciatic nerve, with an independent origin and course of the tibial and common fibular nerve). This anatomical variation may have clinical importance, as it may be, for example, a risk factor to unsuccessful sciatic nerve popliteal blocks and to the pyriformis syndrome.
authors.affiliation: Instituto de Anatomia Normal, Faculdade de Medicina, Universidade de Coimbra, Coimbra, Portugal.
authors.forename: Paulo
authors.initials: P
authors.lastname: Coelho
authors.forename: Catarina
authors.initials: C
authors.lastname: Melo
authors.forename: António
authors.initials: A
authors.lastname: Bernardes
mesh_terms: D000368:Aged; D002102:Cadaver; D006801:Humans; D008297:Male; D010543:Peroneal Nerve / Q000002:abnormalities; D012584:Sciatic Nerve / Q000002:abnormalities*; D013979:Tibial Nerve / Q000002:abnormalities